A类：
子网数目 占用位数子网掩码子网中主机数
　2　1255．128．0．08,388,606
　4　2255．192．0．04,194,302
　8　3255．224．0．02,097,150
　16 4255．240．0．01,048,574
　32 5255．248．0．0524,286
　64 6255．252．0．0262,142
　1287255．254．0．0131,070
　1288255．255．0．065,534

B类：
子网数目 占用位数子网掩码子网中主机数
　2　1255．255．128．0　32,766
　4　2255．255．192．0　16,382
　8　3255．255．224．0　8,190
　16 4255．255．240．0　4,094
　32 5255．255．248．0　2,046
　64 6255．255．252．0　1,022
　1287255．255．254．0　510
　2568255．255．255．0　254

C类：
子网数目 占用位数子网掩码子网中主机数
　2　1255．255．255．128　126
　4　2255．255．255．192　62
　8　3255．255．255．224　30
　16 4255．255．255．240　14
　32 5255．255．255．248　6
　64 6255．255．255．252　2

Table 1.1. CIDR子网表

子网掩码CIDR名称IP数量可用IP数量C类网络的数量255.255.255.255/32111/256255.255.255.254/31201/128255.255.255.252/30421/64255.255.255.248/29861/32255.255.255.240/2816141/16255.255.255.224/2732301/8255.255.255.192/2664621/4255.255.255.128/25128126一半255.255.255.0/242562541255.255.254.0/235125102255.255.252.0/22102410224255.255.248.0/21204820468255.255.240.0/204096409416255.255.224.0/198192819032255.255.192.0/1816,38416,38264255.255.128.0/1732,76832,766128255.255.0.0/1665,53665,534256255.254.0.0/15131,072131,070512255.252.0.0/14262,144262,1421024255.248.0.0/13524,288524,2862048255.240.0.0/121,048,5761,048,5744096255.224.0.0/112,097,1522,097,1508192255.192.0.0/104,194,3044,194,30216,384255.128.0.0/98,388,6088,388,60632,768255.0.0.0/816,777,21616,777,21465,536254.0.0.0/733,554,43233,554,430131,072252.0.0.0/667,108,86467,108,862262,144248.0.0.0/5134,217,728134,217,7261,048,576240.0.0.0/4268,435,456268,435,4542,097,152224.0.0.0/3536,870,912536,870,9104,194,304192.0.0.0/21,073,741,8241,073,741,8228,388,608128.0.0.0/12,147,483,6482,147,483,64616,777,2160.0.0.0/04,294,967,2964,294,967,29433,554,432